The present invention relates to determining the solids content in a solid-liquid mixture, and more particularly to determining the percent of solids content in a solids-liquid mixture by measuring the speed of sound in the solids-liquid mixture.
Many various industrial processes use a solids-liquid mixture either as an interim step or as an end product. It is important for a consistent end product that the percent of solids in the slurry be accurately controlled. Of course, the solids content must be accurately determined before it can be controlled.
One heretofore known method of determining the solids content in a slurry is to extract a sample of the slurry from a production process. The sample is weighed, then dried to eliminate the liquid, and the resulting residue of solids weighed. The weight of the residue of solids is compared to the weight of the slurry sample which gives the percent of solids in the slurry sample. This method takes a substantial period of time. Theoretically, from a quality control standpoint, during the time it takes to determine the solids content in the slurry sample, the production process should be suspended. Production downtime, however, is non-productive and adds to the cost of the end product. Realistically, the production process is usually continued while the testing process is being done even though the solids content in the production slurry may be deviant from the desired level. Another drawback with this testing method is that the slurry sample is not necessarily truly representative of the entire slurry. Yet a further drawback is that, because the production process is continuing during the time it takes to determine the solids content in the slurry sample, by the time the solids content of the sample is determined the percent of solids in the production slurry may have changed from the time the slurry sample was taken. In other words, the solids determining process does not render a "real time" measurement of the solids content in the slurry.
It is known that the solids content in a solid-liquid mixture can be determined by measuring the speed of sound through the mixture. However, these heretofore known ultrasonic measuring systems and methods are limited by the temperature of the mixture and percent of solids in the mixture. These systems and methods seem to be limited to measuring the solids content in a solids-water slurry having a maximum temperature of from about 130.degree. F. to 140.degree. F., and to accurately measure the solids content in a slurry having from about 1% to 6% solids.